JP2013141058A - Relay server and relay communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a relay server that makes access by a communication partner effective without informing the communication partner of an actual address.SOLUTION: A relay server 3 stores the addresses of object terminals 31, 32, 33 and the addresses of operation PCs 11, 12. The relay server 3 exchanges a routing object address with a relay server 1, and establishes a routing session. The relay server 3 transmits a virtual address to the operation PC 11 by email. The relay server 3 relays communication between the object terminals 31, 32, 33 and the operation PCs 11, 12 by using the virtual address together with the relay server 1.

Description

  The present invention mainly relates to a relay server that enables communication between devices connected to different LANs (Local Area Networks).

  2. Description of the Related Art Conventionally, a communication technique called a virtual private network (VPN) that performs communication between LANs installed at physically separated locations is known. In the example shown in Patent Document 1, a relay server, a communication terminal, and the like are connected to each of a plurality of LANs installed at physically separated positions. A communication terminal can transmit a packet to a communication terminal connected to another LAN using this VPN. Specifically, a packet transmitted by a communication terminal is first sent to a relay server in the same LAN. This relay server transmits (transfers) the packet to the relay server in the same LAN as the destination communication terminal via the Internet. The relay server that receives this packet transmits (transfers) the packet to the destination communication terminal.

  By using this VPN, other remote LANs can be used as if they were directly connected networks. In addition, as a usage form of VPN, for example, a configuration in which a remote desktop is used to operate another LAN communication terminal, and a browser is used to browse the contents of another LAN communication terminal (server) Etc. are considered.

JP 2010-268312 A

  By the way, in this type of system, terminals communicate with each other using private IP addresses of terminals connected to the LAN (hereinafter sometimes simply referred to as addresses). Therefore, when performing communication using VPN, it is necessary to transmit the address set in its own LAN to the LAN on the other side.

  In this regard, for example, when building a VPN between the same companies, it is unlikely that a problem will occur even if the address is known to the other party. However, when a VPN is constructed between different companies, it is not preferable that the other party knows the address from the viewpoint of security. Therefore, there has been a demand for a configuration capable of operating the VPN without the addresses assigned to the terminals connected to the LAN being known to other LANs.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a relay server that enables the access of the communication partner without notifying the communication partner of the actual address.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

  According to a first aspect of the present invention, a relay server having the following configuration is provided. That is, the relay server includes an address filter information storage unit and a control unit. The address filter information storage unit is located in the first LAN (the relay server) is capable of transferring packets, and the first routing target address that is the address of the first routing target device and the second relay server located in the second LAN Stores the second routing target address that is the address of the second routing target device that can transfer the packet. The control unit transmits the first routing target address to the second relay server, receives the second routing target address from the second relay server, and establishes a routing session with the second relay server. The control unit transmits the virtual address assigned to the first routing target address to the second routing target device by electronic mail. The control unit, together with the second relay server that performs the conversion from the virtual address to the first routing target address or the conversion from the first routing target address to the virtual address, Relay communication with the second routing target device.

  As a result, the user who operates the second routing target device can access the first routing target device by using the virtual address sent by e-mail. Therefore, the first and second routing target devices can communicate with each other without notifying the second routing target device of the actual address of the first routing target device. Even when the address of the first routing target device is changed, communication can be continued only by changing the assignment relationship of the virtual address stored in the second relay server. Moreover, since an electronic mail is used, a virtual address can be transmitted only to a predetermined second routing target device with a simple configuration.

  The relay server preferably has the following configuration. That is, an expiration date can be set for the virtual address assigned to the first routing target address. Further, the virtual address that has passed the expiration date cannot access the first routing target device.

  As a result, it is possible to prevent a situation in which a connection to the first routing target device is continued indefinitely, and thus security can be improved. In addition, since the present invention is configured to notify the virtual address by electronic mail, if the electronic mail is intercepted, unauthorized access may be performed. In this respect, the above-described configuration has an expiration date set, so that this unauthorized access can be prevented.

  The relay server preferably has the following configuration. That is, a plurality of virtual addresses are assigned to one first routing target address. The virtual address that the control unit transmits to the second routing target device by e-mail is different for each second routing target device or for each user.

  Thereby, for example, when the control unit transmits a different virtual address for each second routing target device, access to the first routing target device can be restricted for each second routing target device. On the other hand, when the control unit transmits a different virtual address for each user, access to the first routing target device can be restricted for each user.

  According to the 2nd viewpoint of this invention, the relay communication system of the following structures is provided. That is, the relay communication system includes a first relay server and a second relay server. The first relay server located in the first LAN includes an address filter information storage unit and a control unit. The address filter information storage unit includes a first routing target address that is an address of a first routing target device to which the first relay server can transfer a packet, and the second relay server located in a second LAN transfers the packet. And a second routing target address that is an address of a possible second routing target device. The control unit is configured to transmit the first routing target address to the second relay server, receive the second routing target address from the second relay server, and establish a routing session with the second relay server. And a control for transmitting the virtual address assigned to the first routing target address to the second routing target device by e-mail. When the second relay server receives a packet destined for the virtual address from the second routing target device, the second relay server converts the destination address of the packet into the first routing target address corresponding to the virtual address. Transfer the packet to the routing session. When the second relay server receives a packet destined for the second routing target address from the routing session, the second relay server converts the packet source address to the virtual address assigned to the second routing target address. Then, the packet is transferred to the destination second routing target apparatus.

  Accordingly, the first and second routing target devices can communicate with each other without notifying the second routing target device of the actual address. Further, even when the address of the first routing target device is changed, communication can be continued appropriately only by changing the assignment relationship of the virtual address stored in the second relay server.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows the whole structure of the relay communication system which concerns on one Embodiment of this invention. The functional block diagram of a relay server. The figure which shows the content of relay group information. The figure which shows the content of relay server information. The figure which shows the content of client terminal information. The figure which shows the content of VPN group information. The figure which shows the content of the address filter information registered beforehand in each relay server. The figure which shows the address filter information and virtual address which the relay servers 1 and 3 memorize | store after construction of VPN. The figure which shows the content of the virtual address registration information of the relay server 1. FIG. The figure which shows the content of the virtual address time limit information of the relay server 1. FIG. The flowchart which shows the setting performed to a relay server beforehand. The flowchart which shows the process which produces a VPN group. The flowchart which shows the process which builds VPN. The flowchart which shows the process which builds VPN. The flowchart which shows the routing control which a relay server performs when a packet is received from LAN. The flowchart which shows the routing control which a relay server performs when a packet is received from a routing session. Explanatory drawing which shows the condition when communicating using the said virtual address after notifying a virtual address. The figure explaining the structure which changes a virtual address for every user which concerns on a modification.

  Next, embodiments of the present invention will be described with reference to the drawings. First, an overview of the relay communication system 100 of the present embodiment will be described with reference to FIG. FIG. 1 is an explanatory diagram showing the overall configuration of the relay communication system 100 according to the present embodiment.

  As shown in FIG. 1, this relay communication system 100 includes a plurality of LANs 10, 20, and 30 connected to a wide area network (WAN) 80. Each of the LANs 10, 20, and 30 is a relatively small network constructed in a limited place. Further, the LANs 10, 20, and 30 are arranged at locations that are physically separated from each other. In the present embodiment, the Internet is used as the WAN 80.

  Each LAN will be specifically described below. As shown in FIG. 1, a relay server (second relay server) 1, operation PCs 11 and 12 as second routing target devices, and a client terminal 13 are connected to a LAN (second LAN) 10. . A relay server 2, an operation PC 21, and a client terminal 22 are connected to the LAN 20. Connected to the LAN (first LAN) 30 are a relay server (first relay server) 3, target terminals 31, 32 and 33 as first routing target devices, and a client terminal 34.

  Since each of the relay servers 1, 2, and 3 is connected not only to the LANs 10, 20, and 30 but also to the WAN 80, it can communicate with devices connected to the same LAN and is also arranged in another LAN. It is also possible to communicate with the relay server. The operation PCs 11, 12, and 21 are personal computers that are operated by an operator, for example. The target terminals 31, 32, and 33 are personal computers or file servers. For example, the operator operates the operation PC 11 or the like to request predetermined data from the target terminal 31 or the like, and the target terminal 31 It is assumed that the stored content of is updated. The client terminals 13, 22, and 34 are configured by, for example, a personal computer, and can communicate with each other via the relay servers 1, 2, and 3 to which the client terminals 13, 22, and 34 belong.

  Next, a detailed configuration of the relay servers 1, 2, and 3 will be described with reference to FIG. FIG. 2 is a functional block diagram of the relay server 3. Since the relay server 3 has substantially the same configuration as the relay servers 1 and 2, the relay server 3 will be mainly described below.

  As illustrated in FIG. 2, the relay server 3 includes a storage unit 50, a control unit 60, and an interface unit 70.

  The interface unit 70 performs communication with terminals in the LAN 10. The interface unit 70 performs communication with the WAN 80. The interface unit 70 performs an appropriate process on the packet received from the LAN 30 or the WAN 80 and outputs the packet to the control unit 60.

  The control unit 60 is a CPU having control and calculation functions, for example, and can execute various processes by a program read from the storage unit 50. The control unit 60 can control various communications according to protocols such as TCP / IP, UDP, and SIP. Specifically, the control unit 60 determines a destination of the received packet based on information indicated by the packet and information stored in the storage unit 50, and transmits the packet to the determined destination. Moreover, the control part 60 can update the memory content of the memory | storage part 50 based on the information received from the other terminal.

  The storage unit 50 is composed of, for example, a hard disk or a nonvolatile RAM, and can store various data. The storage unit 50 includes a relay group information storage unit 51, a relay server information storage unit 52, a client terminal information storage unit 53, a VPN group information storage unit 54, an address filter information storage unit 55, and a virtual address registration information storage. Unit 56 and virtual address allocation information storage unit 57. Hereinafter, the contents stored in the storage unit 50 will be described with reference to FIGS. 3 to 10 are diagrams showing the storage contents of the storage unit 50 such as the relay server 1.

  The relay group information storage unit 51 stores relay group information indicating a relay group and a relay server that constitutes the relay group.

  As shown in FIG. 3, in the relay group information, a group tag and a site tag of a child element whose parent element is the group tag are described. In the group tag, group information 511 related to the relay group is described. As the group information 511, relay group identification information (“id”), last update time (“lastmod”), and relay group name (“name”) are described. In the site tag, group configuration information 512 related to the relay server that configures the relay group is described. In this group configuration information 512, identification information (“id”) of the relay server is described. Further, additional relay groups can be created. In this case, unique identification information different from other relay groups is given to the new relay group. As a result, settings such as data exchange only within a specific relay group are possible.

  This relay group information is shared between the relay servers 1, 2, and 3 that constitute the relay group. When a process for changing a relay group is performed in a certain relay server, the fact is transmitted to the other relay server and the relay group information is updated. In this way, relay group information is dynamically shared.

  The relay server information storage unit 52 stores relay server information indicating an outline of a relay server that performs relay communication and a client terminal that belongs to the relay server.

  In the relay server information shown in FIG. 4, a site tag described for each relay server and a node tag of a child element whose parent element is the site tag are described. In the site tag, server information 521 regarding the relay server 1 is described. As the server information 521, relay server identification information (“id”), a relay server name (“name”), and activation information (“stat”) are described. When the content of “stat” is “active”, it indicates that the relay server is logged in to the relay communication system 100, and when stat is blank, it indicates that the log-off is being performed. In a node tag that is a child element of the site tag, affiliation information 522 indicating a client terminal belonging to the relay server is described. The belonging information 522 includes the name of the relay group to which it belongs (“group”), the identification information of the client terminal (“id”), the name of the client terminal (“name”), and the identification information of the relay server to which it belongs. ("Site"). When the client terminal is not logged in to the relay communication system 100, “site” is blank.

  Note that the communication by the relay group is performed as follows based on the relay group information and the relay server information. For example, when a packet is transmitted from the client terminal 13 to the client terminal 22, the client terminal 13 first transmits the packet to the relay server 1 that is a relay server to which the client terminal 13 is connected. The relay server capable of exchanging packets can be grasped based on the above relay group information, and the identification information of the client terminal belonging to the relay server and the connection possibility can be determined based on the above relay server information. I can grasp it. Based on these pieces of information, the relay server 1 transfers the packet to the relay server 2 that is a relay server to which the client terminal 22 is connected. The relay server 2 that has received this packet transfers the packet to the client terminal 22. Thus, relay communication can be performed between the client terminals 13 and 22.

  As with the relay group information, the relay server information is shared between the relay servers 1, 2, and 3 that constitute the relay group. When a process for changing the relay server information is performed in a certain relay server, the fact is transmitted to the other relay server and the relay server information is updated. In this way, the relay server information is dynamically shared.

  The client terminal information storage unit 53 stores client terminal information that is detailed information about the client terminal. Note that the relay servers 1, 2, and 3 store only client terminal information related to client terminals belonging to the relay server. Since the client terminal 34 belongs to the relay server 3, only the client terminal information about the client terminal 34 is stored in the client terminal information storage unit 53 provided in the relay server 3.

  The client terminal information stored in the client terminal information storage unit 53 of the relay server 3 is shown in FIG. Similarly, the client terminal information stored in the relay server 1 is shown in FIG. 5A, and the client terminal information stored in the relay server 2 is shown in FIG. 5B.

  In the client terminal information shown in FIG. 5, a node tag is described. The node tag includes a private IP address (“addr”) of the client terminal, a name of the relay group to which the client terminal belongs (“group”), identification information (“id”), a name (“name”), a relay A password for logging in to the server (“pass”) and port information (“port”) are described.

  The VPN group information storage unit 54 stores VPN group information, which is information related to a VPN group configured by a relay server and a device selected as a routing point from the client terminal (hereinafter referred to as a routing device). ing. By establishing a routing session between routing devices belonging to the same VPN group, communication using VPN can be started.

  In the VPN group information shown in FIG. 6, a vnet tag is described. In this vnet tag, VPN group basic information 541, routing point information 542, and routing session information 543 are described. The VPN group basic information 541 includes a relay group name (“group”) to which the VPN group belongs, a VPN group identification information (“id”), a last update time (“lastmod”), and a VPN group name. ("Name"). The routing point information 542 describes identification information of a routing device that performs routing when communication is performed between VPN groups. In the example of FIG. 6, a relay server 1 and a relay server 3 are described as routing devices. The routing session information 543 describes routing devices connected to each other in the VPN group. In the routing session information 543, the routing device first performs communication control (“sp (start point)”) in the routing session establishment process for establishing the VPN in the VPN group and starting communication, and its communication. It is determined separately for the control side (“ep (end point)”). In the following description, a routing device that first performs communication control for establishing a routing session may be referred to as a “start point”, and a routing device that receives the communication control may be referred to as a “end point”.

  It can be seen from the VPN group information shown in FIG. 6 that the VPN group (VPN-GROUP 1) is composed of the relay server 1 and the relay server 3. It can also be seen that at the start of this VPN group, communication control for establishing a routing session from the relay server 3 to the relay server 1 is performed.

  This VPN group information is also shared between the relay servers 1 and 3 belonging to the same VPN group, like the relay server information and the relay group information. When a process for changing VPN group information is performed in a certain relay server, the fact is transmitted to other relay servers belonging to the same VPN group, and the VPN group information is updated. In this way, VPN group information is dynamically shared. The process for creating this VPN group will be described later.

  The address filter information storage unit 55 stores address filter information that is information used when performing routing control using VPN. The address filter information storage unit 55 stores information (address filter information of the relay server 3) indicating a device (routing target device) to which the relay server 3 itself can directly transmit a packet before the VPN is constructed. The address filter information includes the address of the routing target device (routing target address) and the name of the routing target device.

  FIG. 7C shows an example of address filter information registered in advance in the relay server 3 itself. In this example, it is described that devices to which the relay server 3 can directly transmit packets are the target terminals 31, 32, and 33. 7A shows the address filter information registered in advance in the relay server 1, and FIG. 7B shows the address filter information registered in advance in the relay server 2.

  As described above, the address filter information storage unit 55 of the relay server 3 stores only the address filter information shown in FIG. 7C before constructing the VPN. When the relay server 3 establishes a routing session with the relay server 1, for example, the relay server 3 transmits address filter information (FIG. 7C) registered in advance to the relay server 1 and addresses from the relay server 1. The filter information (FIG. 7A) is received. Then, the relay server 3 stores the address filter information of the relay server 1 in the address filter information storage unit 55 in association with the identification information of the relay server 1.

  As a result, the contents shown in FIG. 8B are stored in the address filter information storage unit 55 of the relay server 3. Similarly, the same content (the same content as FIG. 8B) is also stored in the address filter information storage unit 55 of the relay server 1. Then, the relay servers 1 and 3 perform routing control based on the acquired address (detailed control will be described later). Hereinafter, a routing target address (addresses of target terminals 31, 32, and 33) included in the address filter information of the relay server 3 is referred to as a first routing target address, and the routing target included in the address filter information of the relay server 1 The address (the address of the operation PCs 11 and 12) may be referred to as a second routing target address.

  In the present embodiment, in the communication between the relay server 1 and the operation PCs 11 and 12, communication is performed using a virtual address without using the actual addresses of the target terminals 31, 32, and 33. As the virtual address, an address that does not overlap in the LAN 10 (an address that is not assigned to a device in the LAN 10 and that is not reserved) is registered in advance and stored in the virtual address registration information storage unit 56 of the relay server 1. Has been. In the present embodiment, the addresses shown in FIG. 9 are registered as virtual addresses.

  In the present embodiment, in the communication between the relay server 3 and the target terminals 31, 32, 33, communication is performed using the actual addresses of the operation PCs 11, 12, but a virtual address is used as in the relay server 1. It may be configured to perform communication using.

  The relay server 1 exchanges the address filter information as described above and acquires the addresses of the target terminals 31, 32, and 33 from the relay server 3, and then assigns a virtual address to the address. The virtual address allocation information storage unit 57 of the relay server 1 stores a correspondence relationship (allocation relationship) between the received address and the virtual address, as shown in FIG.

  The virtual address deadline information storage unit 58 of the relay server 1 stores an expiration date set for each virtual address as shown in FIG. The expiration date may be set for each virtual address allocation. Further, the expiration date may be renewable in the middle.

  Next, preparation for performing communication using VPN will be described. First, the setting performed in advance on the relay server will be described with reference to FIG. 11, and the flow when creating a VPN group will be described with reference to FIG. FIG. 11 is a flowchart showing settings to be made to the relay server in advance. FIG. 12 is a flowchart showing processing for creating a VPN group. In the following, the relay server 1 is taken as an example, and the settings performed on the relay server and the processing executed by the relay server 3 will be described. Can be executed.

  The setting to be made in advance in the relay server 3 includes registration of address filter information of the relay server 3 (S101). This registration is performed by a user using the relay communication system 100 by inputting an address (first routing target address) of a device or the like designated as a routing target device and a name by a predetermined method. Here, it is assumed that the user has input the addresses and names of the target terminals 31, 32, and 33. The registered address filter information is stored in the address filter information storage unit 55.

  Next, when performing communication using a virtual address, the user registers an address that does not overlap within the LAN 30 to which the relay server 3 is connected as a virtual address (S102). The virtual address registered here is stored in the virtual address registration information storage unit 56.

  Hereinafter, the flow when creating a VPN group will be described. First, the user can display a VPN group setting screen by operating the client terminals 13, 22, 34, and the like. Here, a case where setting is performed using the client terminal 34 will be described. On the setting screen displayed on the client terminal 34, a plurality of relay groups to which the client terminal 34 belongs are displayed. The user selects a relay group for which a VPN group is to be constructed from the plurality of relay groups (S201).

  When a relay group is selected, a list of identification information of relay servers and client terminals that belong to the selected relay group and that can function as a routing point is displayed on the screen of the client terminal 34 (S202). Then, the user selects a relay server and a client terminal that function as a routing point in the VPN group to be constructed (S203). In this description, it is assumed that the relay server 1 and the relay server 3 are selected by the user.

  Then, based on the identification information of the selected relay server, the identification information of the routing point and the routing session information are created (S204). The VPN group information shown in FIG. 6 is created by adding VPN group identification information or the like to these pieces of information. The client terminal 34 transmits this VPN group information to the relay servers 1 and 3 belonging to the same VPN group (S205). Then, the relay servers 1 and 3 store the received VPN group information in the VPN group information storage unit 54. Thus, the VPN group construction process is completed.

  Next, a flow until communication using VPN is started in the constructed VPN group will be described with reference to FIGS. 13 and 14. FIG. 13 and FIG. 14 are flowcharts showing processing performed until communication using VPN is started.

  The user can display the constructed VPN group on the screen by operating the client terminal 13 or the operation PC 11 or the like. Then, by selecting an appropriate VPN group from the displayed VPN groups (S301), a process for constructing the VPN can be performed. In this description, an example will be described in which the relay server 3 performs the start process of the VPN group created above (a VPN group composed of the relay servers 1 and 3).

  The relay server 3 first reads out address filter information associated with itself (S302). The information read here is the content registered in S101 (the content shown in FIG. 7C). Next, the relay server 3 reads the routing points belonging to the selected VPN group (S303). Thereby, the relay server 1 is read based on the content of the VPN group information shown in FIG.

  Based on the relay server information, the relay server 3 first determines whether the relay server 1 is logged in (“stat” is active or blank) (S304). According to the relay server information shown in FIG. 4, since the relay server 1 is logged in, the relay server 3 transmits a VPN group start command together with the VPN group identification information to the relay server 1 (S305).

  When the relay server 3 receives a response from the relay server 1 in response to the start command (S306), the relay server 1 registers the relay server 1 as a routing point that is ready to construct a VPN (S307).

  Next, the relay server 3 determines whether there is another device belonging to the same VPN group (S308). Since the currently created VPN group is composed of only the relay server 1 and the relay server 3, there is no other device. If there is another device, the relay server 3 performs the processing of S304 to S307 this time for the device.

  Next, the relay server 3 extracts routing session information from the contents stored in the VPN group information storage unit 54 (S309 in FIG. 14). Then, the relay server 3 refers to the extracted routing session information, and determines whether or not a routing session starting from itself is described (S310). In the routing session information of FIG. 6, it is described that in the routing session to be established between the relay server 1 and the relay server 3, itself (the relay server 3) is the starting point.

  Therefore, the relay server 3 establishes a routing session by performing predetermined communication control on the relay server 1 (S311). When performing this communication control, the address filter information is exchanged as described above (S312). Thereby, the contents shown in FIG. 8B are stored in the address filter information storage unit 55 of the relay server 3. Further, the relay server 1 acquires the addresses of the target terminals 31, 32, and 33 from the relay server 3 and assigns a virtual address to the address. As a result, the contents shown in FIG. 8A are stored in the address filter information storage unit 55 of the relay server 1.

  Next, the relay server 3 acquires the correspondence relationship (allocation relationship) between the addresses of the target terminals 31, 32, and 33 and the virtual address from the relay server 1 (S313). Instead of the configuration in which the relay server 3 acquires the allocation relationship from the relay server 1, a configuration in which the relay server 3 creates the allocation relationship and transmits the allocation relationship to the relay server 1 may be employed. In this case, the relay server 1 assigns a virtual address based on the received assignment relationship.

  Next, the relay server 3 performs the process of S310 again. Since the currently created VPN group is composed of only the relay server 1 and the relay server 3, other routing sessions are not described in the VPN group information. Accordingly, the relay server 3 starts packet routing control (S314). If there is another routing session, the relay server 3 performs the processes of S311 to S313 again.

  As described above, in this embodiment, when a VPN is constructed, each routing device exchanges (acquires) address filter information with other routing devices. Therefore, the VPN is constructed using the latest address filter information. Can do. Therefore, even if the address filter information is changed in some routing devices at the stage before the VPN start, the VPN can be constructed and communication can be started with the change reflected in all the routing devices. Inconsistency in routing can be prevented, and reliability can be improved.

  Each routing device does not perform the initial communication control for establishing a routing session unless the routing session information indicates that it is the starting point. The routing session can be established with simple control.

  Next, a process for routing a packet using the established routing session will be described. Hereinafter, the relay server 1 will be described as an example, and the processing executed by the relay server 1 will be described. However, the relay servers 2 and 3 can also execute the same processing.

  First, control performed when the relay server 1 receives a packet from the LAN 10 will be described with reference to FIG. FIG. 15 is a flowchart showing the flow of this control.

  The relay server 1 stands by until a packet is received from the LAN 10 (S401). When a packet is received from the LAN 10, it is first determined whether or not the destination of the packet is itself (relay server 1) (S402).

  When the destination of the packet is itself, the relay server 1 receives the packet (S403). On the other hand, when the destination of the packet is other than itself, the relay server 1 compares the destination address of the received packet with the address filter information (see FIG. 8A), and the destination address is the address filter. It is determined whether or not the information is registered (S404). When the destination address is not registered in the address filter information, the relay server 1 discards the packet (S405). On the other hand, when the destination address is registered in the address filter information, the relay server 1 specifies a routing session corresponding to the address filter information (S406).

  Next, the relay server 1 refers to the virtual address assignment information storage unit 57 and determines whether or not the destination address is a virtual address (S407). If the destination address is a virtual address, the relay server 1 converts the destination address into an actual address (S408), and transmits (transfers) the packet to the routing session specified in S406 (S409).

  Next, control performed when the relay server 1 receives a packet from the routing session will be described with reference to FIG. FIG. 16 is a flowchart showing the flow of this control.

  The relay server 1 stands by until a packet is received from the routing session (S501). When the relay server 1 receives the packet, the relay server 1 compares the destination address of the packet with the address filter information (see FIG. 8A), and the packet destination address becomes the address filter information of its own. It is determined whether or not they are registered in association (S502).

  When the destination address of the packet is registered in association with its own address filter information, the relay server 1 refers to the virtual address assignment information storage unit 57 and determines whether or not a virtual address is assigned to the source address. (S503). When a virtual address is assigned to the transmission source address, the relay server 1 converts the transmission source address into a virtual address (S504), and transfers the packet to the device (operation PC 11, 12) indicated by the destination address (S505). ). When a virtual address is not assigned to the transmission source address, the relay server 1 transfers the packet to the device indicated by the destination without converting the address (S505).

  Further, when the destination address is not registered in association with its own address filter information, the relay server 1 determines whether the destination address is registered in association with the address filter information of another routing device. This is performed (S506). When the destination address is registered in association with the address filter information of another routing device, the relay server 1 identifies the corresponding routing session (S507), and transmits (forwards) the packet to this routing session ( S508).

  On the other hand, when the destination address is not registered in the address filter information of another routing device, the relay server 1 discards the packet (S509).

  By performing the above control, communication can be performed using a virtual address.

  Next, a flow when the operation PC 12 and the target terminal 31 exchange packets via the relay servers 1 and 3 that perform the above control will be described with reference to FIG.

  When permitting the operation PC 12 (or a user who operates the operation PC 12) to access the target terminal 31, the relay server 3 transmits an e-mail to the operation PC 12, as illustrated in FIG. In this e-mail, the virtual address of the target terminal 31 acquired from the relay server 1 by the relay server 3 in S313 is described. In addition to describing the virtual address directly as the IP address of the access destination in the electronic mail, the virtual address can be described in an appropriate format such as a URL format.

  When the user who operates the operation PC 12 desires access to the target terminal 31, as shown in FIG. 17B, based on the received electronic mail, a packet having the virtual address as the destination address is transmitted. The relay server 1 that has received this packet performs the control shown in FIG. That is, the relay server 1 identifies the routing session by recognizing that the relay server 3 is described as the routing device corresponding to the destination address of the packet based on the address filter information (see FIG. 8A). (S406). Next, the relay server 1 recognizes that the destination address is a virtual address, and converts the destination address into an actual address (S408). Then, the relay server 1 transmits (transfers) the packet to the relay server 3 via the routing session (S409).

  The relay server 3 that has received this packet recognizes that itself (the relay server 3) is described as a routing device corresponding to the destination address of the packet based on the address filter information (see FIG. 8B). To do. Then, the relay server 3 transmits (transfers) the packet to the destination target terminal 31.

  Next, as shown in FIG. 17C, the target terminal 31 transmits a reply packet corresponding to the received packet to the relay server 3 with the address of the operation PC 12 as the destination address. The relay server 3 that has received this packet recognizes that the relay server 1 is described as a routing device corresponding to the destination address of the packet. And the relay server 3 performs the process which transmits a packet to the relay server 1 via a routing session.

  The relay server 1 that has received this packet performs the control shown in FIG. That is, the relay server 1 recognizes that itself (the relay server 1) is described as a routing device corresponding to the destination address of the packet based on the address filter information (see FIG. 8A). Then, the relay server 1 refers to the virtual address assignment information storage unit 57 and recognizes that the virtual address is assigned to the transmission source address. Then, the relay server 1 converts the transmission source address into a virtual address (S504), and transmits the packet to the destination operation PC 12 (S505).

  As described above, packets can be exchanged without notifying the operation PC 12 of the actual address of the target terminal 31. Thereby, security can be improved. Further, for example, even when the actual address of the target terminal 31 needs to be changed, it is only necessary to update the allocation relationship stored in the relay server 2, which saves the trouble of changing the settings of the operation PCs 11 and 12. it can.

  As described above, the relay server 3 according to this embodiment includes the address filter information storage unit 55 and the control unit 60. The address filter information storage unit 55 stores the first routing target address (addresses of the target terminals 31, 32, and 33) and the second routing target address (addresses of the operation PCs 11 and 12). The control unit 60 exchanges routing target addresses with the relay server 1 to establish a routing session. The control unit 60 transmits the virtual address to the operation PCs 11 and 12 by electronic mail. The control unit 60 relays communication between the target terminals 31, 32, 33 and the operation PCs 11, 12 using the virtual address together with the relay server 1.

  Thereby, the user who operates the operation PCs 11 and 12 can access the target terminals 31, 32, and 33 by using the virtual address sent by the e-mail. Therefore, communication can be performed without notifying the operation PCs 11 and 12 of the actual addresses of the target terminals 31, 32 and 33. Further, even if the addresses of the target terminals 31, 32, and 33 are changed, communication can be continued only by changing the allocation relationship of the virtual addresses stored in the relay server 1. Moreover, since an electronic mail is used, a virtual address can be transmitted only to the selected one of the operation PCs 11 and 12.

  Next, a modification of the above embodiment will be described. FIG. 18 is a diagram illustrating a configuration in which a virtual address is different for each user according to the modification.

  In the above embodiment, the relay server 1 is configured to assign one virtual address to each of the addresses of the target terminals 31, 32, and 33. On the other hand, in this modification, the relay server 1 is configured to assign a plurality of virtual addresses to the addresses of the target terminals 31, 32, and 33, respectively. Examples of assigning a plurality of virtual addresses include, for example, a configuration in which different virtual addresses are assigned for each routing target device to which an e-mail is transmitted, and a configuration in which different virtual addresses are assigned for each user account. Hereinafter, the latter configuration will be described as a representative.

  As shown in FIG. 18, in this modification, the virtual addresses assigned to the target terminals 31, 32, and 33 are different between the operator A1 and the operator A2. Also, the expiration date of the virtual address is different for each operator.

  Each operator has an e-mail address associated with his / her account, and the e-mail transmitted to his / her e-mail address regardless of which operation PC 11 or 12 is used. It shall be possible to receive mail.

  Thus, the user on the LAN 10 side can grasp which operator is communicating based on the destination address of the transmitted packet. Therefore, it is possible to restrict access to the operator rather than the routing target device.

  The preferred embodiments and modifications of the present invention have been described above, but the above configuration can be modified as follows, for example.

  An IPv6 format IP address may be used instead of the IPv4 format IP address. In this case, the virtual address may be IPv6 as well.

  The timing for assigning the virtual address is arbitrary. For example, the address filter information may be exchanged together with the transmission of the start command, and the virtual address may be assigned immediately thereafter.

  In the above, only the relay server functions as a routing point. However, the client terminal may function as a routing point. Further, the number of routing points in the VPN group is not limited to two and may be three or more. One routing device may belong to a plurality of VPN groups.

  The format for storing the relay group information, relay server information, client terminal information, VPN group information, address filter information, etc. is not limited to the XML format, and each information can be stored in an appropriate format.

  Instead of the above-described configuration, an external server used for communication between each relay server may be installed on the Internet, and a communication may be performed by exhibiting a function as a SIP (Session Initiation Protocol) server.

1 Relay server (second relay server)
3 Relay server (first relay server)
11, 12 Operation PC (second routing target device)
31, 32, 33 Target terminal (first routing target device)
10 LAN (second LAN)
30 LAN (first LAN)
54 VPN Group Information Storage Unit 55 Address Filter Information Storage Unit 56 Virtual Address Registration Information Storage Unit 57 Virtual Address Assignment Information Storage Unit 60 Control Unit 100 Relay Communication System

Claims (4)

A first routing target address that is an address of a first routing target device that is located in the first LAN and can transfer a packet, and an address of a second routing target device that can be transferred by a second relay server located in the second LAN An address filter information storage unit for storing the second routing target address,
A control unit,
The controller is
A control for transmitting the first routing target address to the second relay server, receiving the second routing target address from the second relay server, and establishing a routing session with the second relay server;
Control for transmitting a virtual address assigned to the first routing target address to the second routing target device by e-mail;
The first routing target device and the second routing target together with the second relay server that converts the virtual address to the first routing target address or the first routing target address to the virtual address. Control to relay communication with the device;
The relay server characterized by performing. The relay server according to claim 1,
An expiration date can be set for the virtual address assigned to the first routing target address,
The relay server, wherein the virtual address that has passed the expiration date cannot access the first routing target device. The relay server according to claim 1 or 2,
A plurality of virtual addresses are assigned to one first routing target address;
The relay server, wherein the virtual address transmitted by the control unit to the second routing target device by e-mail is different for each second routing target device or for each user. In the relay communication system including the first relay server and the second relay server,
The first relay server located in the first LAN is
A first routing target address which is an address of a first routing target device to which the first relay server can transfer a packet, and a second routing target device to which the second relay server located in the second LAN can transfer a packet. An address filter information storage unit that stores a second routing target address that is an address;
Transmitting the first routing target address to the second relay server, receiving the second routing target address from the second relay server, and establishing a routing session with the second relay server; and A control unit that performs control to transmit a virtual address assigned to one routing target address to the second routing target device by e-mail;
The second relay server is
When a packet destined for the virtual address is received from the second routing target device, the destination address of the packet is converted to the first routing target address corresponding to the virtual address, and the packet is transferred to the routing session. Control to
When a packet destined for the second routing target address is received from the routing session, the source address of the packet is converted to the virtual address assigned to the second routing target address, and the second destination address Control to forward packets to the routing target device;
A relay communication system.

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